Whitebark pine declines may unravel the tree's mutualism with Clark's Nutcracker

[PhysOrg]

The relationship between the whitebark pine (Pinus albicaulis), an iconic tree of western mountaintops, and the Clark's Nutcracker (Nucifraga columbiana), a brash bird in the crow family, is often used as an example of the biological concept of mutualism: a relationship between species where both benefit. The pine provides large, nutritious seeds to the nutcracker. The nutcracker buries these seeds for later use in scattered hiding spots, inevitably failing to retrieve some and effectively planting the next generation of whitebark pine. But the mutualism between the pine and the nutcracker is not equal. While the pine depends heavily on nutcrackers for seed dispersal and germination, the nutcracker merely prefers the whitebark pine's seeds. If whitebark pine seeds aren't available or abundant, the highly mobile nutcracker will fly off and find another food source.

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